title: Impaired decline in renal threshold for glucose during pregnancy - a possible novel mechanism for gestational diabetes mellitus.
abstract: BACKGROUND
  The renal threshold for glucose (RT(G)) is determined by the nephron's reabsorptive capacity. Glucose is reabsorbed through sodium-coupled glucose cotransporters in the proximal tubules. During pregnancy, renal glucose reabsorptive capacity decreases, possibly, due to reduced glucose transporter expression. Our hypothesis is that inadequate decrease in RT(G) during pregnancy will make women more prone to develop gestational diabetes mellitus (GDM).
  
  
  METHODS
  Pregnant women (n = 40) who were referred to our center for oral glucose tolerance test (OGTT) were included in the analysis. Plasma glucose levels and urinary glucose excretion were measured for 4 h after 100 g oral glucose load. These data were used to calculate RT(G) . The subjects were divided into two cohorts, GDM and non-GDM, according to the OGTT results. Mean RT(G) was compared between the two groups.
  
  
  RESULTS
  Fifteen (37.5%) of the women were diagnosed with GDM. Seventeen participants had only trace amounts of urinary glucose excretion, and no value of RT(G) could be determined; RT(G) was determined in the other 23 subjects. Among these 23 women, 13 were diagnosed as GDM, and 10 had normal OGTT. RT(G) was lower in the non-GDM women (146 ± 14 mg/dL) than in the GDM women (182 ± 18 mg/dL), p < 0.001.
  
  
  CONCLUSIONS
  Gestational diabetes mellitus is associated with higher RT(G) during pregnancy compared with non-GDM. These results support our hypothesis that inadequate decrease of the RT(G) may have a pathophysiological role in the development of GDM.
authors.affiliation: Diabetes and Endocrinology Unit, Hillel Yaffe Medical Center, Hadera, Israel.
authors.forename: Pinchas
authors.initials: P
authors.lastname: Klein
authors.forename: David
authors.initials: D
authors.lastname: Polidori
authors.forename: Orit
authors.initials: O
authors.lastname: Twito
authors.forename: Anat
authors.initials: A
authors.lastname: Jaffe
mesh_terms: D000042:Absorption; D000328:Adult; D001786:Blood Glucose / Q000032:analysis / Q000378:metabolism*; D015331:Cohort Studies; D016640:Diabetes, Gestational / Q000453:epidemiology / Q000209:etiology*; D004056:Differential Threshold; D005260:Female; D005951:Glucose Tolerance Test; D006029:Glycosuria / Q000209:etiology; D006801:Humans; D007557:Israel / Q000453:epidemiology; D007687:Kidney Tubules, Proximal / Q000378:metabolism / Q000503:physiopathology*; D011247:Pregnancy; D011263:Pregnancy Trimester, Third; D011446:Prospective Studies; D051437:Renal Insufficiency / Q000097:blood / Q000378:metabolism / Q000503:physiopathology* / Q000652:urine; D012307:Risk Factors
chemical_list: D001786:Blood Glucose
keywords: gestational diabetes mellitus; glucose homeostasis; glucose tolerance test; glucosuria; renal threshold for glucose; sodium-coupled glucose cotransporters